The invention relates to a synchroniser ring for a synchronising device of a shiftable change speed gear transmission as well as to a manual transmission for a vehicle in accordance with the preamble of the independent claims 1 and 10.
In a mechanical, shiftable change speed gear transmission, e.g. in vehicle transmissions, synchroniser rings serve to synchronize the relative speeds which occur between the gear wheel and the gear shaft on a gear change to one another. The synchronisation is achieved by friction between the corresponding friction partners. The function of such transmissions and the process of the synchronisation procedure are known per se and no longer have to be explained in more detail to the person skilled in the art here.
It is known for protection against premature wear and/or to improve the friction characteristic to provide the friction surfaces of synchroniser rings with a friction layer, said synchroniser rings being produced as a rule from a metal or a metal alloy such as from brass or steel. Very different types of friction layers are in use in this connection, e.g. thermal injection layers made of molybdenum, carbon friction layers or friction layers made from other materials.
A support for a conical synchroniser ring is described in DE 35 19811 A1 which has an outer sprocket ring divided into three and is arranged in a cylindrical hollow space of a synchroniser ring hub, which is also frequently called a synchroniser ring member, and is anchored substantially rotationally fixedly to the synchroniser ring hub via abutments which are formed as lobes. Substantially rotationally fixedly within the context of this application means that, with the exception of small angle excursions in the peripheral direction, the synchroniser ring is rotationally fixedly connected to the synchroniser ring hub.
DE 198 53 856 A1 describes a further development of the previously described synchroniser ring, with the synchroniser ring of DE 198 53 856 A1 being characterised in that its width is substantially only determined by the required width of its friction surface. This is achieved in that an abutment, which corresponds to the lobes in accordance with DE 35 19811 A1 in function, is arranged at or close to an end portion of the ring member with a smaller conical diameter and in that the contour of the abutment in the radial direction projects beyond the contour of the outer jacket surface of the ring member.
Both synchroniser rings are admittedly basically properly secured by the lobes or abutments against a rotation with respect to the synchroniser ring hub in the operating state, but both lack a reliable guidance in the radial direction in the cylindrical hollow space in the synchronous ring hub.
This means the synchroniser rings known from the prior art are admittedly secured against a rotation in the peripheral direction with respect to the synchronous ring hub, but these rings tend increasedly to uncontrolled movements due to their conical outer shape which cooperates with a cylindrical inner contact surface in the cylindrical hollow space of the synchroniser ring hub, e.g. to small radial excursions or tilt movements which can be expressed e.g. in unpleasant vibrations, and thus have a negative effect on the reliability and precision of the synchronisation process, which can result in an increase in the shifting times, in faster and increased wear of the friction surface and of the total synchroniser ring as such, and thus in shorter repair and service intervals, quite apart from the fact that the shifting and driving comfort of a motor vehicle is considerably restricted by the poor guidance of the synchroniser ring in the hollow space of the synchroniser ring hub and the uncontrolled movements resulting therefrom. These effects become all the more significant, the more power or torque has to be shifted by a corresponding transmission.